The invention relates to a process for the preparation of .gamma.-butyrolactams, which have a useful antiamnesic action.
It is known that Rutaceae Clausena anicata is used as a folk medicine in certain parts of Africa (I. Mester et al., Planta Medica, 32, 81 (1977)). It is also known that the crude extract of Clausena indica Oliv. has a cardiovascular activity, and that two coumarin derivatives, clausmarin A and B, isolated from Clausena pentaphalla (Roxb.) by thin layer chromatography have a spasmolytic activity (Dhan Prakash et al., Phyochem., 17, 1194 (1978); and Aboo Shoeb et al., J. Chem. Soc., Chem. Commun., 1978, 281). The aqueous extract of leaves of Clausena Lansium (lour) Skeels is also regarded in Chinese folk medicine as an effective agent which protects the liver and is employed against acute and chronic viral hepatitis. It has been possible to isolate (.+-.)3(S*),4(R*),5(R*),7(S*)-3-hydroxy-5-.alpha.-hydroxybenzyl-1-methyl-4 -phenylpyrrolidin-2-one (clausenamide) from this extract as one of the main constituents.
Clausenamide and the derivatives prepared from clausenamide show an antiamnesic action and an action affording protection from cerebral hypoxia in animal experiments. Since larger amounts of substance are required for further pharmacological studies, and on the other hand only 1.5 g of starting compound can be obtained from 4 kg of dried leaves by the expensive extraction process, it was necessary to provide a process for chemical synthesis.